The invention relates to a flotation plant, particularly, but not exclusively, for coal separating equipment, in which a liquid stream containing solid particles to be floated and other solid particles not to be floated is gassed to form gas bubble/solid particle complexes with the solid particles to be floated, and in which the gassing stream is divided to separate the solid particles which are to be floated from those which are not.
The invention is of particular use in the flotation of very small particles from pulpy streams. It can thus be used to good effect for separating out foreign matter from liquids which contain the foreign matter in very small concentrations; this problem arises mainly in the purification of waste water.
These application possibilities for the invention derive from the construction of the flotation plant. A spatial separation can be provided between a conditioning plant for the stream and the place where the gas bubbles are added to the solid particles to be floated, and between the gassing appliance provided for this purpose and the formation of froth and the separation of the froth formed. In this way the mechanical and hydromechanical conditions which prevail at any given time in the separate stages of such a plant can be used to the optimum effect for the treatment process concerned. This means that in the gassing appliance, conditions are created under which the attachment of the solid particles to the gas bubbles and the generation of contact forces which exceed the repulsing forces are achieved. These conditions are created by the use of reagents or appropriate gases which bind with the solid particles to be floated but not with the solid particles to remain in solution. In the subsequent treatment stages, conditions different from these can be created, whereby amongst other things it can be ensured that the de-foaming of the gas bubble--solid matter complexes can be carried out without dangerous break-down forces arising.